help-Powerhead is dogey

[Fish Friend]

hi,
i have a aquaclear 20 powerhead in my 10 gallon with a sponge attached to it, for some reason over the past few weeks its been acting pretty dogey, the bit where it sucks air in isnt working even when i put it on full flow, the flow of the powerhead goes down very quickly, i cleaned it top to bottom last night, when i turned it on it was fine, but this morning its really slow again and kind of clicking??, can anyone think why its doing this?
ive ad it for quite a few months but it shouldnt be not working now!
thanks in advance

 

[Orion]

check the impeller and make sure that it's not warped or damaged. Also remove the impeller from the impeller shaft and make sure the shaft is clean and free of any debris. Also ensure the impeller chamber is clean.

 

[Fish Friend]

what shall i look for when im checking if its not warped?? i clean the impeller chamber and its perfectly clean?